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Distributed space-frequency coding for cooperative diversity in broadband wireless ad hoc networks

IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2008年第3期7卷 995-1003页

作者： Zhang, Wei Li, Yabo Xia, Xiang-Gen Ching, P. C. Ben Letaief, Khaled Hong Kong Univ Sci & Technol Dept Elect & Comp Engn Kowloon Hong Kong Peoples R China Univ Delaware Dept Elect & Comp Engn Newark DE 19716 USA Chinese Univ Hong Kong Dept Elect Engn Sha Tin Hong Kong Peoples R China

w A distributed space-frequency (SF) coded cooperative technique is proposed for broadband wireless ad-hoc networks, where both the channels from the source node to relay nodes and from the relay nodes to the destination node are characterized by frequency-selective fading. Using an SIT coding at the source node and a circular shift at each relay node, we propose a scheme that can achieve both cooperative and multipath diversity. The pairwise error probability is analyzed and the result demonstrates that a diversity gain of min(ML1, ML2) can be achieved, where All is the number of the relay nodes, and L, and L-2 are the number of taps of the multipath fading channels from the source node to the relay nodes and from the relay nodes to the destination node, respectively. Furthermore, the proposed distributed SF coding can achieve full-rate transmission for any number of relay nodes. In particular, it does not need IFFT/FFT processing or decoding at each relay node, thus providing a low-complexity design of the relay nodes in broadband wireless ad-hoc networks.

关键词： cooperative diversity multipath channels relay channels space-frequency coding

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On the Performance of a Constellation-rotated Time-spreaded space-frequency coding Scheme for 4 x 1 MISO OFDM Transceivers

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WIRELESS PERSONAL COMMUNICATIONS 2011年第2期60卷 251-262页

作者： Senthuran, S. Anpalagan, A. Das, O. Khan, S. Ryerson Univ Dept ELCE Toronto ON Canada Khulna Univ ECE Discipline Khulna Bangladesh

In this article, we propose a time-spreaded quasi-orthogonal space-frequency coded OFDM system with constellation rotation. A constellation rotated quasi-orthogonal OFDM system could offer full rate and full diversity in a frequency selective fading channel. Time spreading can give additional time diversity gain in a fast fading channel. Assuming that complex channel gains between adjacent subcarriers are approximately equal, we develop a coding scheme for 4 x 1 MISO transceiver and its BER performance is evaluated for different Doppler frequencies in an OFDM system. The simulation results show that 2 dB gain can be achieved at BER of 10(-3) using the proposed scheme compared to a scheme without time spreading and constellation rotation when 512 subcarriers are used at maximum Doppler frequency of 300 Hz. Also, the proposed system is analyzed for different delay spread of the channel and the results show that if adjacent subcarriers are correlated, it is better in SF-OFDM decoding.

关键词： OFDM MISO space-frequency coding Time spreading Constellation rotation BER performance Doppler frequency

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Distributed space-frequency coding over Broadband Relay Channels

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2008年第11期7卷 4748-4759页

作者： Seddik, Karim G. Liu, K. J. Ray Univ Alexandria Dept Elect Engn Alexandria 21544 Egypt Univ Maryland Dept Elect & Comp Engn College Pk MD 20742 USA Univ Maryland Syst Res Inst College Pk MD 20742 USA

Designing diversity achieving schemes over the wireless broadband fading relay channels is crucial to achieve higher diversity gains. These gains are achieved by exploiting the multi-path (frequency) and cooperative diversities to combat the fading nature of wireless channels. The challenge is how to design space-frequency codes, distributed among randomly located nodes that can exploit the frequency diversity of the wireless broadband channels. In this paper, the design of distributed space-frequency codes (DSFCs) for wireless relay networks is considered. The proposed DSFCs are designed to achieve the frequency and cooperative diversities of the wireless relay channels. The use of DSFCs with the decode-and-forward (DAF) and amplify-and-forward (AAF) protocols is considered. The code design criteria to achieve full diversity, based on the pairwise error probability (PEP) analysis, are derived. For DSFC with the DAF protocol, a two-stage coding scheme, with source node coding and relay nodes coding, is proposed. We derive sufficient conditions for the proposed code structures at the source and relay nodes to achieve full diversity of order NL, where N is the number of relay nodes and L is the number of paths per channel. For the case of DSFC with the AAF protocol, a structure for distributed space-frequency coding is proposed.

关键词： Amplify-and-forward broadband channels decode-and-forward relay channels space-frequency coding

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Distributed space-frequency coding for Cooperative Diversity Over Broadband Relay Channels With DF Relaying

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2012年第7期61卷 3266-3272页

作者： Al-nahari, A. Y. Seddik, K. G. Dessouky, M. I. Abd El-Samie, F. E. Ibb Univ Fac Engn & Architecture Dept Elect Engn Ibb Yemen Amer Univ Cairo Dept Elect Engn New Cairo 11835 Egypt Menoufia Univ Fac Elect Engn Dept Elect & Elect Commun Menoufia 32952 Egypt

Multipath fading is one of the main challenges in transmission over wireless broadband relay channels due to frequency selectivity, which may deteriorate the received signal. Exploiting the extra source of multipath diversity, aside from cooperative (user) diversity, is important when coping with these wireless channel limitations. In this correspondence, we propose a new distributed space-frequency code (SFC) for broadband fading relay channels that can exploit both the spatial and multipath diversities in a distributed fashion. An upper bound for pairwise error probability (PEP) is derived, and from this PEP bound, we show that the proposed code achieves a diversity of order NL, where N is the number of relay nodes, and L is the channel memory length. The decode-and-forward (DF) protocol and erroneous decoding at the relay nodes are considered. Moreover, it is shown that the proposed code structure achieves the maximum coding gain among the linearly coded systems over channels with uniform power delay profiles.

关键词： Broadband relay channels cooperative diversity decode and forward (DF) space-frequency coding

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LDPC based differential unitary space-frequency coding for MIMO-OFDM systems

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2005年第6期6卷 294-298页

作者：姜海宁罗汉文田继锋宋文涛刘兴钊 Department of Electronic Engineering Shanghai Jiaotong University Shanghai 200030 China

This paper proposes a novel LDPC based differential unitary space-frequency coding (DUSFC) scheme for MIMO-OFDM systems when neither the transmitter nor the receiver has access to the channel state information (CSI). The new DUSFC strategy basically consists of coding across transmit antennas and OFDM tones simultaneously as well as differential modulation in the time-domain. It can fully exploit the inherent advantages provided by the multipath fading channels, resulting in a high degree of diversity. The state-of-the-art low-density parity-check (LDPC) codes are concatenated with our DUSFC as channel coding to improve the bit error rate (BER) performance considerably. Owing to the maximum multipath diversity and large coding advantages, LDPC-DUSFC strongly outperforms the differential unitary space-time coded OFDM techniques re- cently proposed in literature. The corresponding iterative decoding algorithm without channel estimation is finally provided to offer significant performance gain. Simulation results illustrate the merits of the proposed scheme.

关键词： Differential modulation Unitary space-time codes space-frequency coding MIMO OFDM LDPC

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Alamouti-based space-frequency coding for OFDM

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WIRELESS PERSONAL COMMUNICATIONS 2005年第1-2期35卷 173-185页

作者： Hutter, AA Mekrazi, S Getu, BN Platbrood, F CSEM CH-2000 Neuchatel Switzerland Inst EURECOM F-06904 Sophia Antipolis France Univ Aalborg DK-9220 Aalborg Denmark

We investigate space-frequency block coding for OFDM systems with multiple transmit antennas, where coding is applied in the frequency domain (OFDM carriers) rather than in the time domain (OFDM symbols). In particular we consider Alamouti's code, which was shown to be the optimum block code for two transmit antennas and time domain coding. We show that the standard decoding algorithm results in significant performance degradation depending on the frequency-selective nature of the transmission channels, such that a low coherence bandwidth results in a huge degradation. The optimum decoding algorithm that alleviates this problem is the maximum-likelihood decoder for joint symbol detection. We present a performance analysis for the investigated space-frequency decoders in terms of the achievable BER results. Furthermore we compare space-time and space-frequency coding and discuss the respective advantages and drawbacks of the different decoding algorithms in terms of their complexity. It should be noted that for the space-time approach we introduce the so-called matched-filter receiver, which shows significantly lower complexity compared to the maximum-likelihood decoder known from literature. The HIPERMAN system serves as an example OFDM system for quantitative comparisons.

关键词： space-frequency coding joint maximum-likelihood detection/decoding transmit diversity OFDM

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Cooperative space-frequency coding for Broadband Relay Channels

Cooperative Space-Frequency Coding for Broadband Relay Chann...

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International Conference on Computer Engineering and Systems

作者： Al-nahari, Azzam Y. Seddik, Karim G. Dessouky, Moawad I. Abd El-Samie, Fathi E. Menoufia Univ Dept Elect & Elect Commun Fac Elect Engn Menoufia 32952 Egypt Univ Alexandria Dept Elect Engn Alexandria Egypt

ISBN: (纸本)9781424458424

In this paper, a new distributed space-frequency coding (DSFC) scheme, for broadband fading relay channels is presented. This scheme exhibits a spatial and a multipath diversity in a distributed fashion. An upper-bound on the pairwise error probability (PEP) is derived. From this PEP bound, it is shown that the proposed coding scheme achieves a diversity of order NL, where N is the number of relay nodes and L is the channel memory length. A decode-and-forward (DAF) protocol and erroneous decoding at the relay nodes are considered. To compensate for the diversity loss due to potential error detection at the relay nodes, additional coding at the source node is proposed.

关键词： Decode-and-forward frequency-selective channel OFDM relay channel space-frequency coding

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Performances of differential-encoded FFHMA systems with space-frequency coding over Nakagami-m fading channels

Performances of differential-encoded FFHMA systems with spac...

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60th IEEE Vehicular Technology Conference

作者： Khemapatapan, C Benjapolakul, W Chulalongkorn Univ Dept Elect Engn Bangkok 10330 Thailand

ISBN: (纸本)0780385217

Performances and capacities of differential-encoded fast frequency-hopping multiple-access (FFHMA) systems under Nakagami-m fading channels are studied. The space-frequency coding (SFC) scheme is applied to gain diversity order. The proposed FFHMA transmitter can operate without an output hopping filter. The simulation results show that the receiver can detect the transmitted signal when maximum Doppler frequency closes to 350 Hz. The performances of synchronous FFHMA systems can be improved by spreading factor and average SNR per bit. In Rayleigh fading channel, the system capacity of FFHMA for BER about 10(-3) is derived from simulation and it is about 5, 24, and 61 users for spreading factor of 1, 2, and 4 respectively.

关键词： fast frequency-hopping multiple-access space-frequency coding Nakagami-m fading channel

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Virtual MIMO Schemes for Downlink space-frequency coding OFDM Systems

Virtual MIMO Schemes for Downlink Space-Frequency Coding OFD...

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20th IEEE Symposium on Personal, Indoor and Mobile Radio Communications

作者： Teodoro, Sara Silva, Adao Gil, Joao M. Gameiro, Atilio Univ Aveiro Inst Telecomunicacoes P-3800 Aveiro Portugal

ISBN: (纸本)9781424451234

In this paper we investigate the performance of single-relay cooperative scheme, where the source is equipped with a 2-antenna array and both the relay and destination with a single antenna. We consider Amplify-and-Forward, Decode-and-Forward and Selective Decode-and-Forward relaying protocols and a space-frequency block coding designed for DL OFDM based systems is employed. Signals expressions are derived for each relay protocol under various scenarios, considering power constraint imposed on cooperating nodes. The aim of this work is to evaluate this Virtual MIMO scheme in realistic scenarios (e. g. correlated antennas, precise channel models, Doppler effects) for implementation purposes in a system with LTE based parameters and considering channel turbo coding. The coded performance of the proposed Virtual MIMO scheme is evaluated, and compared against non-cooperative OFDM based systems, for typical pedestrian scenarios based on LTE specifications. The proposed cooperative scheme outperforms the co-located MISO and MIMO for some scenarios.

关键词： Virtual MIMO cooperative diversity OFDM space-frequency coding relaying protocols

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Alamouti-based space-frequency coding for OFDM

Alamouti-based space-frequency coding for OFDM

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International Symposium on Wireless Personal Multimedia Communications

作者： Hutter, AA Mekrazi, S Getu, BN Platbrood, F CSEM CH-2000 Neuchatel Switzerland Inst EURECOM F-06904 Sophia Antipolis France Univ Aalborg DK-9220 Aalborg Denmark

关键词： space-frequency coding joint maximum-likelihood detection/decoding transmit diversity OFDM

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